'When all this is over,' wrote poet Kathleen Jamie, 'I mean to travel north/ by the high drove roads and cart tracks/ probably in June/ with the gentle dog rose/ flourishing beside me.' 'This', in the poem 'Lochan', is the maelstrom of family life and the goal Jamie imagines is an isolated loch and a boat. Sara Maitland, too, felt this pull into the 'Great Nothing' and, after 20 years as a vicar's wife and 'noisy' - and acclaimed - feminist novelist, embarked on a quest for silence which took her to ever more isolated and northern houses: in Northamptonshire, County Durham and, finally, her native Galloway.

On the way, she experimented with more extreme forms of isolation - Zen meditation, a flotation tank, a week in the Sinai Desert - and defined the particular sort of silence she was after: solitude, with inspiring landscape. Now she lives alone on a moor and frequently unplugs the phone.

These are all unusual things to do. They are not, though, as strongly countercultural as Maitland is keen to suggest. It is not true that 'as a society we will do anything we can to avoid silence at every level' or that 'we are terrified of silence and try to banish it from our lives'. We may lack silence but many of us also yearn for it. Madonna meditates; celebrities live on country estates and would like us to try their cheeses; entire issues of Granta are devoted to meditations on the landscape. A Book of Silence itself builds on the huge success of books by Roger Deakin and Robert Macfarlane.

We do lack, though, a practical rather than romantic guide to silence and here Maitland comes into her own. Oddly for a Roman Catholic who prays for three hours a day, she is often more convincing on the body than the spirit. Her own body is warmly present throughout the book, and we come to know and like her through it; this tall, rangy woman who hasn't had her haircut for 25 years, who has to stop for a smoke, who salivates for porridge and sweats in shopping malls, who meditates squatting on a dictionary and who prefers embroidery to knitting because it doesn't make 'that irritating click-clack noise'.

Some of the most memorable parts of the book are her exact, visceral accounts of the effects of prolonged solitude: the lassitude stage (so dangerous in the desert); the disinhibition phase (when you pick your nose while eating); the heightened senses experience; and the bit when you hear Latin choirs singing in the bedroom.

Maitland makes a convincing case for these being universal responses, demonstrating similar patterns in the logbooks of round-the-world yachtsmen and the journals of explorers and prisoners. Mostly of men, in other words. Despite her radical feminist past, Maitland seems drawn to the athletic, epic, masculine sort of solitude-seeking rather than the mystical self-immuring of women. She gives pages to St Anthony and the desert fathers, for instance, but only half a line to Julian of Norwich and the English anchorites, most of a chapter to the Golden Globe Yacht Race of 1968, but nothing to the celebrated retreat of Emily Dickinson.

But Dickinson and Julian of Norwich are sparse, ironic, enigmatic writers. Maitland is the opposite: generous, expansive, even garrulous. Her sentences are long and liberally sprinkled with a distinctive mixture of old and new-fashioned slang - 'a good deal' and 'totally', 'half-way decent' and 'mindset'. This loose, breezy voice can hit a magnificent rhythm as she strides up hills, but it falters when she approaches the heart of her subject: encounters with the silent sublime. Faced with the infinite, Maitland tends to fall back on the devices of the gap-year emailer: capital letters ('It was NOW'); italics ('The sky was deep'), and single-sentence paragraphs ('The whole night I listened - listened to nothing'). Her prosy field of reference lets her down here too - Jacques Cousteau is a favourite and at one point she illustrates the jouissance born of 40 days in the wilderness with a quote from A Wizard of Earthsea. I wish she could have quoted Kathleen Jamie at that point, or Jen Hadfield or Alice Oswald or Mary Oliver, to name but four contemporary women poets embarked on strikingly similar quests. She should at least have heard of them - they practically constitute a movement. Or that she had winnowed her own frequently lovely images - 'An infinite recession of stars' - from her heaps of prose.

I suspect, though, that Maitland is as wary of literary stylists as of hair stylists, that they bring out in her, like beauty salons, her 'most dour residue of Presbyterian puritanism'. She is not dour at all but is a puritan: she has a compulsive, almost childlike honesty, a horror of affectation or vanity. This makes her, in the end, a trustworthy guide to this spiritual terrain in which it is so easy to pause and admire your own progress. Hers is a true pilgrim soul and, while we may disagree with her conclusions, it is impossible to scoff at her testament.

• Kate Clanchy's latest book, What Is She Doing Here?: A Refugee's Story (Picador), won The Writers' Guild Best Book Award 2008